1. FIELD OF THE INVENTION
This invention relates to a controlled deflection roll such as is used in the press and calender sections of a papermaking machine. More particularly, this invention relates to a self-loading type of controlled deflection roll wherein the roll shell can translate relative to the longitudinal axis of the roll. Still more particularly, this invention relates to a self-loading controlled deflection roll wherein the roll shell is both rotatably and positionably supported solely by hydraulically actuated shoes on a stationary shaft. Even still more specifically, this invention relates to an adjustably positionable side guide shoe apparatus for stabilizing the roll shell in a self-loading type of controlled deflection roll.
2. DESCRIPTION OF THE PRIOR ART
A prior self-loading type of controlled deflection roll is described and illustrated in Biondetti, U.S. Pat. No. 3,885,283. In this patent, the roll shell is hydrostatically supported in the direction of its nip with another roll by a plurality of shoes which are aligned longitudinally along the length of the stationary support shaft. A pair of collars, each having a pair of flat, parallel surfaces, are disposed at either end of the roll shell to slide over corresponding surfaces on the roll shaft to permit the roll shell to translate reciprocally in the direction of its nip with another roll while maintaining the roll shell in a fixed position relative to the shaft in a plane perpendicular to a plane through the nip with another roll. The roll shell rotates on bearings mounted to each of the collars.
Other patented controlled deflection rolls utilize magnets to compensate and adjust for deflection of a rotating, bearing supported roll shell over a stationary support shaft. Still other patents relating to self-loading controlled deflection rolls disclose support of the roll shell relative to the shaft by a plurality of circumferentially spaced shoes which position the rotating roll shell at predetermined radial positions about the roll shaft according to the circumferential position of the roll shaft.
In Arav, U.S. Pat. No. 4,821,384, diametrically opposed nip loading shoes are positioned in the stationary shaft of a controlled deflection roll to move the roll shell radially inwardly and outwardly in opposed directions relative to the shaft. In some embodiments, stabilizing shoes are located circumferentially about the roll shaft outside of the plane of the nip loading shoes which actuate the roll shell. The stabilizing shoes move outwardly relative to the longitudinal axis of the roll shaft and also slide along flat surfaces on the roll shaft parallel to the plane of the support shoes and the nip.
Regardless of the configuration of prior self-loading controlled deflection rolls, none of them can provide constant roll shell stabilizing force in a configuration where the roll shell is not mounted on bearings, or where there are dimensional variations in the roll, or both, particularly in rolls utilizing hydraulically actuated stabilizing shoes. Thus, the prior self-loading type of controlled deflection rolls cannot accommodate dimensional variations between the roll shell and stationary shaft due to manufacturing tolerances and temperature changes which affect different components in different degrees depending on the co-efficient of thermal expansion of their materials. For example, in some prior designs of self-loading rolls, the pressurized hydraulic fluid could escape more quickly from one stabilizing shoe, or at the interface of a stabilizing shoe and the supporting roll shaft at one location than at another. This could cause variations in the stabilizing pressures provided between the shaft and inner surface of the roll shell and thus permit the roll shell to shift its radial position laterally of the plane of the nip, or even to oscillate relative to the shaft.
Further, in some instances, such as when the tolerances become negative, stabilizing shoes interposed between the shaft and roll shell can become wedged between the shaft and roll shell and act as a brake to the detriment of the intended method of operation.